The invention relates primarily to the sheet metal industry in which large quantities of parts are produced for use in the heating and cooling industry. At the present time, blanks are cut from sheet metal in a desired configuration so that the blanks can later be formed into components that are installed as part of a heating, cooling and ventilating system. As is well known to those skilled in the art, air in such systems is conveyed to or from a desired space. The sheet metal components used in such air duct systems are many and varied, and a common one is a boot which is a transition piece that connects a duct of circular cross section to a rectangular outlet. These boots and other components for air conveying systems are produced from flat blanks of sheet metal which are then formed into the desired configuration.
At the present time, blanks are produced by one of two methods. The blanks can be cut from the sheet material by the use of a punch press and die. However, each time it is desired to produce a blank of a different configuration, the die must be changed. This is expensive and time consuming. Also, because the blanks almost always have an irregular configuration, it is usually more efficient to lay out the blanks on the sheet metal so that they "nest", thus reducing the amount of scrap material. With the punch press and die method, the parts cannot be nested, thus resulting in high scrap rates.
A second known method for producing sheet metal blanks is by stacking a number of large pieces of sheet material from which the blanks are to be cut and then cutting them with a band saw. Obviously, this requires the large sheet metal pieces from which the blanks are to be cut to be cut from the coil prior to the sawing operation, and like the punch press and die method, the parts cannot be nested resulting in high scrap rates. Moreover, cutting the blanks with a band saw is noisy and somewhat dangerous, and the accuracy of the cuts is less than desirable, especially where the parts must be cut to relatively close tolerances.
There are also known methods and equipment for cutting blanks from sheet metal using a cutter, such as a plasma torch, that is mounted over a table holding the piece of sheet material from which the blanks are to be cut. The cutter is moved along two perpendicular axes, and movement of the cutter is controlled by a computer program so as to make the desired cuts to produce blanks of the desired configuration. Examples of apparatus employing this method are shown in Levine U.S. Pat. No. 4,551,810 and Levine U.S. Pat. No. 4,554,635. Although the apparatus and methods of the Levine patents have advantages over the use of punch presses or band saws, they were designed for the user who has to produce a relatively small number of sheet metal fittings and other components and who must change frequently the type and size of the blanks which are being cut. However, the methods and machines of the Levine patents cannot produce blanks continuously from a coil of material, and production is slowed somewhat by the necessity to walk around the machine to collect the finished parts and then remove the large pieces of scrap. Moreover, since the plasma torch travels over the entire surface of the table, the table supporting the material as it is cut must be periodically replaced since it becomes damaged each time a cut is made through the sheet material. Also, with a plasma torch cutter, fume removal is difficult.
There is therefore a need for a method and apparatus that will improve upon the prior art methods and machines by providing for the production of sheet metal blanks continuously and automatically at a relatively high rate of production.